JP2023178560A - Method for producing ruthenium thin film or ruthenium compound thin film by chemical vapor deposition process, and ruthenium thin film or ruthenium compound thin film - Google Patents

Abstract

To provide a chemical vapor deposition process that makes it possible to form a high-quality ruthenium thin film or the like while suppressing the oxidation of a substrate.SOLUTION: The present invention relates to a method for producing a ruthenium thin film or a ruthenium compound thin film by a chemical vapor deposition process, where the ruthenium thin film or the ruthenium compound thin film is formed by reacting an organic ruthenium compound with a reaction gas on a substrate. According to the present invention, the chemical vapor deposition process comprises: a first film formation step for using a non-oxidizing gas as a reaction gas; and a second film formation step for forming a film by using an oxidizing gas as a reaction gas after forming the film in the first film formation step. In addition, as the organic ruthenium compound serving as a precursor, any one among predetermined organic ruthenium compounds α, β, and γ containing a carbonyl ligand is used.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a ruthenium thin film or a ruthenium compound thin film by a chemical vapor deposition method (chemical vapor deposition method (CVD method), atomic layer deposition method (ALD method)). Specifically, the present invention relates to a chemical vapor deposition method using a predetermined organic ruthenium compound, which achieves low resistance of a thin film and is excellent in film formation efficiency.

Thin films made of ruthenium or ruthenium compounds (hereinafter referred to as "ruthenium thin films, etc." or simply "thin films") are expected to be used as wiring and electrode materials for semiconductor devices such as DRAMs and FERAMs. This tendency has become more pronounced as wiring becomes finer due to the recent miniaturization of semiconductor devices. Until now, copper has been mainly used as a wiring material for semiconductor devices, but in the wiring of fine semiconductor devices of 10 nm class, the wiring width is smaller than the mean free path of electrons in copper (approximately 38.7 nm). Therefore, when a copper thin film is applied to such fine wiring, the resistance coefficient due to surface scattering and grain boundary scattering, which is proportional to the mean free path, increases and the resistance value (specific resistance) of the wiring increases. On the other hand, since the mean free path of electrons in ruthenium is 10.8 nm, which is much shorter than that in copper, an increase in resistivity due to surface scattering and grain boundary scattering can be suppressed. Further, ruthenium is a high melting point metal (melting point 2250° C.) higher than copper (melting point 1085° C.) and has high electromigration resistance. For these reasons, ruthenium as a wiring material has many advantages, such as lowering the resistance of fine wiring and prolonging the life of the wiring.

Chemical vapor deposition methods such as CVD (chemical vapor deposition) and ALD (atomic layer deposition) are used to manufacture ruthenium thin films and the like. Ruthenium thin films and the like constituting the wiring and electrodes of semiconductor devices, which are becoming increasingly finer, are required to have a dense structure with a high aspect ratio. The ALD method is particularly useful for controlling the fine structure of such thin films. Many organic ruthenium compounds have been known as raw materials (precursors) for producing ruthenium thin films and the like by chemical vapor deposition.

Organic ruthenium compounds, which serve as precursors, have a large impact on the properties of ruthenium thin films, film formation efficiency, etc., and therefore there are many examples of their use. Furthermore, the characteristics required of organic ruthenium compounds are wide-ranging. In the past, issues such as being a liquid at room temperature and having a high vapor pressure were considered for ease of handling and lowering the film-forming temperature, and organic ruthenium compounds that address these issues have become publicly known. Ta. For example, there is bis(ethylcyclopentadienyl)ruthenium (II) shown in Chemical Formula 1 described in Patent Document 1.

Furthermore, in recent years, there has been a demand for expanding the selection range of reaction gases for organic ruthenium compounds that serve as precursors. In the chemical vapor deposition method, a reaction gas is generally introduced into a reactor together with a vaporized organic ruthenium compound. Organic ruthenium compounds can be decomposed by heating alone to deposit a ruthenium thin film, but in that case, the decomposition rate is poor and efficient film formation cannot be expected. Therefore, a reactive gas is introduced to promote the decomposition of the organic ruthenium compound. Organic ruthenium compounds that have been known for a long time, such as the above-mentioned bis(ethylcyclopentadienyl)ruthenium (II), require an oxidizing gas such as oxygen or ozone to be used as a reaction gas. However, the oxidizing gas causes oxidative damage to the substrate. Although there are various materials for the substrate, Cu, W, TiN, etc. are particularly easy to oxidize. Although damage to the substrate due to oxidation is not itself desirable, the generated oxides may deteriorate the properties of the thin film.

Therefore, recent demands for precursors include the use of organic ruthenium compounds that can be decomposed using non-oxidizing gases such as hydrogen and ammonia as reaction gases. The applicant has developed multiple organic ruthenium compounds that can meet these demands. For example, in Patent Document 2, dicarbonyl-bis(5-methyl-2,4-hexanediketonato)ruthenium (II) shown below is listed as an example, and in Patent Document 3, as an example, hexacarbonyl [μ- [(1,2-η)-3-methyl-N-(1-methylpropyl)-1-butene-1-aminato-κC ² ,κN ¹ :κN ¹ ]] diruthenium (Ru-Ru) further contains , Patent Documents 4 and 5 describe (η ⁴ -methylene-1,3-propanediyl)tricarbonylruthenium shown below as an example.

Japanese Patent Application Publication No. 2000-281694 Patent No. 4746141 specification Patent No. 6027657 specification International Publication WO2021/153639 Publication Japanese Patent Application Publication No. 2020-090689

The organic ruthenium compounds of Chemical Formulas 2 to 4 exemplified above are capable of depositing ruthenium using a non-oxidizing gas such as hydrogen as a reaction gas, and oxidation of the substrate is suppressed. However, according to studies by the present inventors, the resistivity of ruthenium thin films formed using non-oxidizing gases using these organic ruthenium compounds may not be sufficiently reduced. In this respect, these organic ruthenium compounds can be formed into films using oxidizing gas, and in some cases, a ruthenium thin film formed using oxidizing gas may have a lower resistance.

Furthermore, when forming a ruthenium thin film or the like using a non-oxidizing gas as a reaction gas, the film forming rate tends to be low. This is because a non-oxidizing atmosphere such as hydrogen is inherently poor in reactivity. The above-described organic ruthenium compounds of Chemicals 2 to 5 enable film formation using non-oxidizing gas such as hydrogen, which is an advantage over conventional organic ruthenium compounds. Compared to film formation in a highly reactive oxidizing gas atmosphere, non-oxidizing gas is inferior in film formation rate. If we aim to achieve high throughput thin film formation, it is also important to improve the film formation rate.

The present invention was made against the above background. The present invention relates to a chemical vapor deposition method for forming a high-quality ruthenium thin film or the like while suppressing oxidation of a substrate. For this purpose, the present invention aims to clarify the factors that increase the specific resistance of a thin film when an organic ruthenium compound that can be formed into a film using a non-oxidizing gas is used as a precursor, and to use chemical vapor deposition to avoid this. This paper proposes a method.

In order to solve the above problem, the present inventors first investigated the factors that increase the specific resistance of ruthenium thin films formed using non-oxidizing gas, and found that the incorporation of impurity elements such as carbon (C) I came up with the idea. Many of the organic ruthenium compounds that make it possible to form a ruthenium thin film or the like in the above-mentioned non-oxidizing gas atmosphere contain a carbonyl ligand (CO) as a ligand. Carbonyl ligands have a high bonding property with ruthenium, but are easily released as gas when the organic ruthenium compound is decomposed, so they are originally suitable ligands. However, in a non-oxidizing gas atmosphere with low reactivity, the release of decomposed components from the reaction system may be delayed and may be mixed into the thin film as impurities. This is considered to be a factor in the increase in specific resistance of the thin film. On the other hand, in an oxidizing gas atmosphere, the decomposed components of the organic ruthenium compound are quickly released from the system due to its good reactivity, and there is little contamination of impurities. However, as described above, oxidizing gas can cause oxidation of the substrate.

Considering the effects of non-oxidizing gases and oxidizing gases on substrates and thin films as described above, non-oxidizing gases can be applied when they are in contact with the substrate, and can be applied to relatively thin thin films with little accumulation of impurities. It can be said that it is useful for film formation. On the other hand, since oxidizing gas is less likely to accumulate impurities, it is suitable for ensuring a film formation rate to obtain a desired film thickness as long as contact with the substrate can be avoided. The present inventors have understood the suitability of each reaction gas as described above, and applied a non-oxidizing gas as a reaction gas in the early stage of film formation as a film formation method using chemical vapor deposition to solve the above problems. They discovered a two-step film-forming process in which a ruthenium thin film or the like is formed on a substrate, and then the thin film is grown using an oxidizing gas as a reactive gas, and the present invention was conceived.

That is, the present invention provides a method for producing a ruthenium thin film or a ruthenium compound thin film by a chemical vapor deposition method in which an organic ruthenium compound and a reactive gas are reacted on a substrate to form a ruthenium thin film or a ruthenium compound thin film. a first film forming step of introducing an oxidizing gas and forming a ruthenium thin film or a ruthenium compound thin film on the substrate surface; and after film formation in the first film forming step, introducing an oxidizing gas as the reaction gas; The organic ruthenium compounds introduced in the first film forming step and the second film forming step include the following organic ruthenium compounds (1) to (3). This is a method for producing a ruthenium thin film or a ruthenium compound thin film, characterized in that one of ruthenium compounds α, β, and γ is applied.

（式中、配位子Ｌ_１は、炭素数２以上１３以下の直鎖又は分枝鎖の鎖状炭化水素基又は環状炭化水素基である。また、配位子Ｘは、カルボニル配位子（ＣＯ）又は下記の化６～化１２の式で示されるイソシアニド配位子（Ｌ_２）、ピリジン配位子（Ｌ_３）、アミン配位子（Ｌ_４）、イミダゾール配位子（Ｌ_５）、ピリダジン配位子（Ｌ_６）、ピリミジン配位子（Ｌ_７）、ピラジン配位子（Ｌ_８）のいずれかである。 (1) Organic ruthenium compound α

(In the formula, the ligand L ₁ is a linear or branched chain hydrocarbon group or a cyclic hydrocarbon group having 2 to 13 carbon atoms. Also, the ligand X is a carbonyl ligand (CO) or isocyanide ligand (L ₂ ), pyridine ligand (L ₃ ), amine ligand (L ₄ ), imidazole ligand (L ₅ ) represented by the following formulas 6 to 12. ), a pyridazine ligand (L ₆ ), a pyrimidine ligand (L ₇ ), or a pyrazine ligand (L ₈ ).

（上記式中、イソシアニド配位子Ｌ_２の置換基Ｒ_１は、水素、炭素数１以上８以下の直鎖若しくは分岐鎖のアルキル基、または炭素数３以上９以下の環状アルキル基、炭素数１以上８以下の直鎖若しくは分岐鎖のアミノ基、炭素数６以上９以下のアリール基、炭素数１以上８以下の直鎖若しくは分岐鎖のアルコキシ基、炭素数１以上８以下の直鎖若しくは分岐鎖のシアノ基、炭素数１以上８以下の直鎖若しくは分岐鎖のニトロ基、炭素数１以上８以下の直鎖若しくは分岐鎖のフルオロアルキル基、のいずれかである。）

(In the above formula, the substituent R ₁ of the isocyanide ligand L ₂ is hydrogen, a linear or branched alkyl group having 1 to 8 carbon atoms, or a cyclic alkyl group having 3 to 9 carbon atoms, or a cyclic alkyl group having 3 to 9 carbon atoms. A straight chain or branched amino group having 1 to 8 carbon atoms, an aryl group having 6 to 9 carbon atoms, a straight chain or branched alkoxy group having 1 to 8 carbon atoms, a straight chain or branched chain having 1 to 8 carbon atoms, (A branched cyano group, a straight or branched nitro group having 1 to 8 carbon atoms, or a straight or branched fluoroalkyl group having 1 to 8 carbon atoms.)

（上記式中、ピリジン配位子Ｌ_３の置換基Ｒ_２～Ｒ_６は、それぞれ、水素、炭素数１以上５以下の直鎖若しくは分岐鎖のアルキル基若しくはフルオロアルキル基、炭素数１以上５以下の直鎖若しくは分岐鎖のフルオロ基、炭素数１以上５以下の直鎖若しくは分岐鎖のアルコキシ基、炭素数１以上５以下の直鎖若しくは分岐鎖のシアノ基、炭素数１以上５以下の直鎖若しくは分岐鎖のニトロ基、のいずれかである。）

(In the above formula, substituents R ₂ to R ₆ of the pyridine ligand L ₃ are hydrogen, a linear or branched alkyl group or fluoroalkyl group having 1 to 5 carbon atoms, and 1 to 5 carbon atoms, respectively. The following straight-chain or branched fluoro groups, straight-chain or branched alkoxy groups with 1 to 5 carbon atoms, straight-chain or branched cyano groups with 1 to 5 carbon atoms, and straight-chain or branched cyano groups with 1 to 5 carbon atoms. Either a straight-chain or branched nitro group.)

（上記式中、アミン配位子Ｌ_４の置換基Ｒ_７～Ｒ_９は、それぞれ、炭素数１以上５以下の直鎖若しくは分岐鎖のアルキル基である。）

(In the above formula, each of the substituents R ₇ to R ₉ of the amine ligand L ₄ is a linear or branched alkyl group having 1 to 5 carbon atoms.)

（上記式中、イミダゾール配位子Ｌ_５の置換基Ｒ_１０は、水素、炭素数１以上８以下の直鎖若しくは分岐鎖のアルキル基、炭素数３以上８以下の環状アルキル基、炭素数１以上８以下の直鎖若しくは分岐鎖のフルオロアルキル基、のいずれかである。置換基Ｒ_１１～Ｒ_１３は、それぞれ、水素、炭素数１以上５以下の直鎖若しくは分岐鎖のアルキル基、炭素数１以上５以下の直鎖若しくは分岐鎖のアミノ基、炭素数１以上５以下の直鎖若しくは分岐鎖のアルコキシ基、炭素数１以上５以下の直鎖若しくは分岐鎖のシアノ基、炭素数１以上５以下の直鎖若しくは分岐鎖のニトロ基、炭素数１以上５以下の直鎖若しくは分岐鎖のフルオロ基、炭素数１以上５以下の直鎖若しくは分岐鎖のフルオロアルキル基、のいずれかである。）

(In the above formula, the substituent R ₁₀ of the imidazole ligand L ₅ is hydrogen, a linear or branched alkyl group having 1 to 8 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, or a carbon number 1 Any of the above 8 or less linear or branched fluoroalkyl groups. Substituents R ₁₁ to R ₁₃ are hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and carbon atoms. Straight chain or branched amino group having 1 to 5 carbon atoms, straight chain or branched alkoxy group having 1 to 5 carbon atoms, straight chain or branched cyano group having 1 to 5 carbon atoms, 1 carbon number Any of a linear or branched nitro group having 5 or more carbon atoms, a linear or branched fluoro group having 1 to 5 carbon atoms, or a linear or branched fluoroalkyl group having 1 to 5 carbon atoms. be.)

（上記式中、ピリダジン配位子Ｌ_６の置換基Ｒ_１４～Ｒ_１７は、それぞれ、水素、炭素数１以上５以下の直鎖若しくは分岐鎖のアルキル基、炭素数１以上５以下の直鎖若しくは分岐鎖のフルオロアルキル基、炭素数１以上５以下の直鎖若しくは分岐鎖のフルオロ基、水素又は炭素数１以上５以下の直鎖若しくは分岐鎖のアルコキシ基、水素又は炭素数１以上５以下の直鎖若しくは分岐鎖のシアノ基、水素又は炭素数１以上５以下の直鎖若しくは分岐鎖のニトロ基のいずれかである。）

(In the above formula, substituents R ₁₄ to R ₁₇ of the pyridazine ligand L ₆ are hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and a linear or branched alkyl group having 1 to 5 carbon atoms, respectively. or a branched fluoroalkyl group, a linear or branched fluoro group having 1 to 5 carbon atoms, hydrogen or a linear or branched alkoxy group having 1 to 5 carbon atoms, hydrogen or a linear or branched alkoxy group having 1 to 5 carbon atoms; is either a straight-chain or branched cyano group, hydrogen, or a straight-chain or branched nitro group having 1 to 5 carbon atoms.)

（上記式中、ピリミジン配位子Ｌ_７の置換基Ｒ_１８～Ｒ_２１は、それぞれ、水素、炭素数１以上５以下の直鎖若しくは分岐鎖のアルキル基、炭素数１以上５以下の直鎖若しくは分岐鎖のフルオロアルキル基、炭素数１以上５以下の直鎖若しくは分岐鎖のフルオロ基、炭素数１以上５以下の直鎖若しくは分岐鎖のアルコキシ基、炭素数１以上５以下の直鎖若しくは分岐鎖のシアノ基、炭素数１以上５以下の直鎖若しくは分岐鎖のニトロ基のいずれかである。）

(In the above formula, the substituents R ₁₈ to R ₂₁ of the pyrimidine ligand L ₇ are hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and a linear or branched alkyl group having 1 to 5 carbon atoms, respectively. or a branched fluoroalkyl group, a linear or branched fluoro group having 1 to 5 carbon atoms, a linear or branched alkoxy group having 1 to 5 carbon atoms, a linear or branched chain having 1 to 5 carbon atoms, or Either a branched cyano group or a straight or branched nitro group having 1 to 5 carbon atoms.)

（上記式中、ピラジン配位子Ｌ_８の置換基Ｒ_２２～Ｒ_２５は、それぞれ、水素、炭素数１以上５以下の直鎖若しくは分岐鎖のアルキル基、炭素数１以上５以下の直鎖若しくは分岐鎖のフルオロアルキル基、炭素数１以上５以下の直鎖若しくは分岐鎖のフルオロ基、炭素数１以上５以下の直鎖若しくは分岐鎖のアルコキシ基、炭素数１以上５以下の直鎖若しくは分岐鎖のシアノ基、炭素数１以上５以下の直鎖若しくは分岐鎖のニトロ基のいずれかである。）

(In the above formula, substituents R ₂₂ to R ₂₅ of pyrazine ligand L ₈ are hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and a linear or branched alkyl group having 1 to 5 carbon atoms, respectively. or a branched fluoroalkyl group, a linear or branched fluoro group having 1 to 5 carbon atoms, a linear or branched alkoxy group having 1 to 5 carbon atoms, a linear or branched chain having 1 to 5 carbon atoms, or Either a branched cyano group or a straight or branched nitro group having 1 to 5 carbon atoms.)

（式中、Ｒ_２６、Ｒ_２７は、互いに同一でも異なっていてもよく、それぞれ、水素原子、炭素数１以上４以下のアルキル基のいずれか１種である。） (2) Organic ruthenium compound β

(In the formula, R ₂₆ and R ₂₇ may be the same or different, and are each one of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms.)

（式中、配位子Ｌ_９は、次式に示される（Ｌ_９－１）又は（Ｌ_９－２）のいずれかで示される配位子であり、１つの窒素原子を含む配位子である。） (3) Organic ruthenium compound γ

(In the formula, the ligand L ₉ is a ligand represented by either (L ₉ -1) or (L ₉ -2) shown in the following formula, and a ligand containing one nitrogen atom. )

（式中、＊は、ルテニウムに橋架け配位する原子の位置である。Ｒ_２８～Ｒ_３５は、互いに同一でも異なっていてもよく、それぞれ、水素原子、炭素数１以上４以下のアルキル基のいずれか１種である。）

(In the formula, * is the position of the atom that bridges and coordinates to ruthenium. _{R 28} to R ₃₅ may be the same or different, and each represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and (1 type)

Hereinafter, a method for manufacturing a ruthenium thin film, etc. by a chemical vapor deposition method and a ruthenium thin film, etc. according to the present invention will be explained in detail.

A. Method for producing a ruthenium thin film, etc., by chemical vapor deposition according to the present invention As described above, the method for producing a ruthenium thin film, etc., according to the present invention includes two stages of film-forming steps using different reaction gases. In the following description, matters common to both film forming steps will be explained, and then each of the first and second film forming steps will be explained.

(a) Basic process of chemical vapor deposition method The present invention is a method of forming a ruthenium thin film etc. by chemical vapor deposition method. The chemical vapor deposition method is a method of manufacturing a thin film by introducing a raw material gas containing a vaporized precursor made of an organic ruthenium compound and a reaction gas onto the substrate surface, decomposing the organic ruthenium compound on the substrate, and precipitating and depositing ruthenium or the ruthenium compound. It is. As chemical vapor deposition methods, chemical vapor deposition methods (CVD methods) and atomic layer deposition methods (ALD methods) are known, depending on the content of supply of raw material gases and reaction gases.

The CVD method is generally a film forming method in which a source gas and a reaction gas are simultaneously introduced onto a substrate and reacted until a thin film with a desired thickness is formed. On the other hand, the ALD method involves a step in which a raw material gas is introduced into a substrate and the raw material compound is adsorbed onto the substrate surface (adsorption step), a step in which excess raw material gas is exhausted (raw material gas purge step), and a reactive gas is introduced into the substrate surface. One cycle includes a series of steps of reacting the adsorbed raw material compound and the reaction gas on the surface to form a thin film (reaction step), and further exhausting the excess reaction gas (reaction gas purge step). This is a thin film forming process in which this cycle is repeated one or more times to achieve a desired film thickness.

The chemical vapor deposition method of the present invention is applicable to both the CVD method and the ALD method. In the CVD method, a raw material gas and a non-oxidizing gas are introduced in the first film-forming process, and a raw material gas and an oxidizing gas are introduced in the second film-forming process. In addition, in the ALD method, the cycle consisting of the above-described adsorption step, raw material gas purge step, reaction step with non-oxidizing gas, and reaction gas purge step is repeated one or more times in the first film formation step, and then in the second film formation step. A cycle consisting of an adsorption step, a raw material gas purge step, a reaction step using an oxidizing gas, and a reaction gas purge step is repeated one or more times to obtain a desired film thickness.

Further, in the chemical vapor deposition method, a thermal CVD method or a thermal ALD method in which a substrate or the like is heated in order to promote the reaction between a raw material compound and a reaction gas is often applied, and the same applies to the present invention. Furthermore, in the chemical vapor deposition method, in addition to assisting by heating, assisting by plasma (PECVD, PEALD), laser, etc. may be performed, and the present invention also uses these in the first film forming step and/or the second film forming step. Applicable.

(b) Substrate There are no particular limitations on the substrate in the present invention. In addition to a Si substrate or a Si/SiO ₂ substrate, any material can be selected depending on the specifications of the device to which it is applied, such as a substrate with a thin film of Cu, W, TiN, etc. on the surface. In particular, since the present invention is based on the premise of suppressing oxidation of the substrate, there is no problem even if the substrate is easily oxidized.

(c) Organic ruthenium compound (precursor)
In the present invention, the organic ruthenium compound serving as the precursor is one that can form a ruthenium thin film or the like when a non-oxidizing gas is used as the reaction gas. This is because a precursor that is not reactive with non-oxidizing gases makes it difficult to form a film in the first film forming step, and the subsequent second film forming step cannot be performed. In the present invention, (1) organic ruthenium compound α (chemical formula 5), (2) organic ruthenium compound β (chemical formula 13), and (3) organic ruthenium compound γ (chemical formula 14) shown above are applied as precursors. . Each organic ruthenium compound will be explained below.

(1) Organic ruthenium compound α
The organic ruthenium compound α is an organic ruthenium represented by Formula 5 above. This organic ruthenium compound has ruthenium (divalent) coordinated with a linear or branched chain hydrocarbon group or a cyclic hydrocarbon group as the ligand _L1 , and further has a ligand X and two It is a compound coordinated with a carbonyl ligand.

As the linear or branched chain hydrocarbon group or cyclic hydrocarbon group having 2 to 13 carbon atoms, which is the ligand L ₁ of the organic ruthenium compound α, the trimethylene ligand (ligand L ₁₀ ), a butadienyl ligand, a pentadienyl ligand, a hexadienyl ligand, a heptadienyl ligand, and the like.

On the other _{hand ,} as _the ligand Any of a ligand (L ₅ ), a pyridazine ligand (L ₆ ), a pyrimidine ligand (L ₇ ), and a pyrazine ligand (L ₈ ) is applied. The specific contents of the ligands L ₂ to L ₈ are as follows.

・Isocyanide ligand (L ₂ )
The isocyanide ligand (L ₂ ) is a ligand represented by the above formula 6. The substituent R ₁ of the ligand L ₂ is hydrogen, a linear or branched alkyl group having 1 to 8 carbon atoms, a cyclic alkyl group having 3 to 9 carbon atoms, and a linear chain having 1 to 8 carbon atoms. or branched amino group, aryl group having 6 to 9 carbon atoms, linear or branched alkoxy group having 1 to 8 carbon atoms, linear or branched cyano group having 1 to 8 carbon atoms, carbon A linear or branched nitro group having 1 to 8 carbon atoms, and a linear or branched fluoroalkyl group having 1 to 8 carbon atoms. _When the _ligand A tert-butyl group, a cyclohexyl group, a trifluoromethyl group, or a pentafluoroethyl group.

・Pyridine ligand (L ₃ )
The pyridine ligand (L ₃ ) is a ligand represented by Formula 7 above. The substituents R ₂ to R ₆ of the ligand L ₃ are hydrogen, a linear or branched alkyl group or fluoroalkyl group having 1 to 5 carbon atoms, and a linear or branched chain having 1 to 5 carbon atoms, respectively. Chain fluoro group, linear or branched alkoxy group having 1 to 5 carbon atoms, linear or branched cyano group having 1 to 5 carbon atoms, linear or branched cyano group having 1 to 5 carbon atoms Nitro group. When the ligand X is a pyridine ligand, all of R ₂ to R ₆ are hydrogen, or R ₂ , R ₄ , and R ₆ are all methyl groups, and R ₃ and R ₅ are hydrogen. or R ₂ and R ₃ and R ₅ and R ₆ are all hydrogen, and R ₄ is a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a trifluoromethyl group, a methoxy group, a cyano group, a nitro group, It is preferable that either of the following is the case.

・Amine ligand (L ₄ )
The amine ligand (L ₄ ) is a ligand represented by Formula 8 above. Each of the substituents R ₇ to R ₉ of the ligand L ₄ is a linear or branched alkyl group having 1 to 5 carbon atoms. When the ligand X is an amine ligand, all of R ₇ to R ₉ are methyl, _ethyl , n-propyl, isopropyl, or n-butyl, Preferably, each of ₈ is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, or a tert-butyl group, and R ₉ is hydrogen.

・Imidazole ligand (L ₅ )
The imidazole ligand (L ₅ ) is a ligand represented by the formula shown in Chemical Formula 9 above. The substituent R ₁₀ of the ligand L ₅ is hydrogen, a linear or branched alkyl group having 1 to 8 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, and a linear chain having 1 to 8 carbon atoms. or a branched fluoroalkyl group. Substituents R ₁₁ to R ₁₃ each represent hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, hydrogen, a linear or branched amino group having 1 to 5 carbon atoms, hydrogen or carbon A linear or branched alkoxy group having 1 to 5 carbon atoms, hydrogen or a linear or branched cyano group having 1 to 5 carbon atoms, hydrogen or a linear or branched nitro group having 1 to 5 carbon atoms , a linear or branched fluoro group having 1 to 5 carbon atoms, hydrogen, or a linear or branched fluoroalkyl group having 1 to 5 carbon atoms. When the ligand X is an imidazole ligand, all of R ₁₀ to R ₁₃ are hydrogen, or R ₁₀ is a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, or a trifluoromethyl group. and R ₁₁ to R ₁₃ are hydrogen, a methyl group, or an ethyl group, or R ₁₀ is a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, or a trifluoromethyl group, and R ₁₁ -R ₁₃ are all hydrogen, a methyl group, or an ethyl group.

・Pyridazine ligand (L ₆ )
The pyridazine ligand (L ₆ ) is a ligand represented by the above formula 10. Substituents R ₁₄ to R ₁₇ of the ligand L ₆ are each hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and a linear or branched fluoroalkyl group having 1 to 5 carbon atoms. group, a straight chain or branched fluoro group having 1 to 5 carbon atoms, hydrogen or a straight chain or branched alkoxy group having 1 to 5 carbon atoms, hydrogen or a straight chain or branched chain having 1 to 5 carbon atoms is either a cyano group, hydrogen, or a linear or branched nitro group having 1 or more and 5 or less carbon atoms. _{When the ligand} , methoxy group, cyano group, or nitro group, and R ₁₅ to R ₁₇ are hydrogen, methyl group, or ethyl group, or R ₁₅ is methyl group, ethyl group, isopropyl group, or tert-butyl group. R ₁₄ , R ₁₆ and R ₁₇ are all hydrogen, methyl group or ethyl group, or both R ₁₅ and R ₁₆ are methyl groups and neither R ₁₄ or R ₁₇ is a group. It is preferable that both hydrogen and hydrogen be used.

・Pyrimidine ligand (L ₇ )
The pyrimidine ligand (L ₇ ) is a ligand represented by the above formula 11. The substituents R ₁₈ to R ₂₁ of the ligand L ₇ are each hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and a linear or branched fluoroalkyl group having 1 to 5 carbon atoms. group, a straight chain or branched fluoro group having 1 to 5 carbon atoms, hydrogen or a straight chain or branched alkoxy group having 1 to 5 carbon atoms, hydrogen or a straight chain or branched chain having 1 to 5 carbon atoms is either a cyano group, hydrogen, or a linear or branched nitro group having 1 or more and 5 or less carbon atoms. _{When the ligand _ _ _ 18} is a methyl group, ethyl group, isopropyl group, tert-butyl group, trifluoro group, fluoro group, methoxy group, cyano group, or nitro group, and R ₁₉ to R ₂₁ are hydrogen, methyl group, or ethyl group or R ₂₀ is either a methyl group, ethyl group, isopropyl group, tert-butyl group, trifluoro group, fluoro group, methoxy group, cyano group, or nitro group, and R ₁₈ and R ₁₉ and R ₂₁ are both hydrogen, methyl group, or ethyl group.

・Pyrazine ligand (L ₈ )
The pyrazine ligand (L ₈ ) is a ligand represented by the above formula 12. The substituents R ₂₂ to R ₂₅ of the ligand L ₈ are each hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and a linear or branched fluoroalkyl group having 1 to 5 carbon atoms. group, a straight chain or branched fluoro group having 1 to 5 carbon atoms, hydrogen or a straight chain or branched alkoxy group having 1 to 5 carbon atoms, hydrogen or a straight chain or branched chain having 1 to 5 carbon atoms is either a cyano group, hydrogen, or a linear or branched nitro group having 1 or more and 5 or less carbon atoms. _{When the ligand} , a methoxy group, a cyano group, or a nitro group, and R ₂₃ to R ₂₅ are hydrogen, a methyl group, or an ethyl group, or R ₂₃ is a methyl group, an ethyl group, an isopropyl group, or a tert-butyl group. group, trifluoromethyl group, fluoro group, methoxy group, cyano group, or nitro group, and whether _R22 , _R24 , and _R25 are all hydrogen, methyl group, or ethyl group. Either case is preferred.

Regarding the above-mentioned combination of _the ligand L ₁ and the ligand Examples include the following organic ruthenium compounds in which the ligand X is carbonyl coordinated (that is, three carbonyl ligands are coordinated).

In this organic ruthenium compound, the substituent R of the trimethylenemethane ligand L ₁₀ is hydrogen, a linear or branched alkyl group having 1 to 8 carbon atoms, or a cyclic alkyl group having 3 to 9 carbon atoms. , a linear or branched alkenyl group having 2 to 8 carbon atoms, a linear or branched alkynyl group having 2 to 8 carbon atoms, a linear or branched amino group having 2 to 8 carbon atoms, carbon An aryl group having a number of 6 or more and 9 or less. More preferably, the substituent R is hydrogen, a linear or branched alkyl group having 2 to 4 carbon atoms, a cyclic alkyl group having 5 to 8 carbon atoms, or a linear or branched chain having 3 to 5 carbon atoms. alkenyl group, a linear or branched alkynyl group having 3 to 5 carbon atoms, a linear or branched amino group having 3 to 5 carbon atoms, or an aryl group having 6 to 8 carbon atoms. .

Specifically, the substituent R of the ligand L ₁₀ is hydrogen, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group (2-methylpropyl), sec-butyl group ( 1-methylpropyl), tert-butyl group (1,1-dimethylethyl), n-pentyl group, isopentyl group (3-methylbutyl), neopentyl group (2,2-dimethylpropyl), sec-pentyl group (1-methylbutyl), tert-pentyl group (1,1-dimethylpropyl), n-hexyl group, isohexyl group (4-methylpentyl), neohexyl group (2,2-dimethylbutyl), sec-hexyl group (1-methylpentyl), tert-hexyl group ( 1,1-dimethylpentyl), cyclohexyl group, cyclohexylmethanyl group, and phenyl group are preferred. More preferred are ethyl group, n-propyl group, n-butyl group, isobutyl group (2-methylpropyl), n-pentyl group, isopentyl group (3-methylbutyl), and neopentyl group (2,2-dimethylpropyl).

(2) Organic ruthenium compound β
The organic ruthenium compound β is an organic ruthenium represented by the above chemical formula 13. This organic ruthenium compound is an organic ruthenium compound in which two β-diketone ligands and two carbonyl ligands are coordinated to ruthenium.

The substituents R ₂₆ and R ₂₇ of the β-diketone ligand are hydrogen or an alkyl group having 1 to 4 carbon atoms. Furthermore, R ₂₆ and R ₂₇ may be the same or different, but are preferably asymmetric γ-diketones that are different from each other. Furthermore, the total number of carbon atoms in R ₂₆ and R ₂₇ is 2 to 5.

(3) Organic ruthenium compound γ
The organic ruthenium compound γ is an organic ruthenium represented by the above formula 14. This organic ruthenium compound is a polynuclear organic ruthenium compound which has two metal-bonded rutheniums as central metals and has a ligand L ₉ bridge-coordinated to ruthenium and a carbonyl ligand as ligands. The ligand L ₉ is a monoimine containing one nitrogen atom, and is either one of the two types of ligands (L ₉ -1) or (L ₉ -2) shown in Formula 16 above. Note that "bridging coordination" refers to steric coordination of two ruthenium molecules so that one ligand bridges them. Specifically, by coordinating to each ruthenium at the two positions indicated by * among the above-mentioned ligands (L ₉ -1, L ₉ -2), (one ligand (to two ruthenium) bridge coordination.

Regarding the substituents R ₂₈ to R ₃₅ of the ligand L ₉ , the total number of carbon atoms of each of the substituents R ₂₈ to R ₃₀ in L ₉ -1 is preferably 3 or more and 10 or less. Further, in L ₉ -2, it is preferable that the total number of carbon atoms in each of the substituents R ₃₁ to R ₃₅ is 2 or more and 10 or less. The substituents R ₂₈ to R ₃₅ may be the same or different, and are each one of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms. When the substituents R ₂₈ to R ₃₅ are alkyl groups, they may be either linear or branched. The alkyl group is preferably any one of a methyl group, an ethyl group, a propyl group, and a butyl group.

The substituents R ₂₈ to R ₃₀ of the ligand L ₉ -1 may be the same or different, and at least one is preferably an ethyl group, a propyl group, or a butyl group. It is also preferable that R ₁ and R ₃ are branched alkyl groups. Specifically, suitable substituents include ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, or tert-butyl group, and are preferred. is an ethyl group, an iso-propyl group, an iso-butyl group, a sec-butyl group, or a tert-butyl group.

R ₂₉ is preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom. These substituents R ₂₉ are located in the steric direction with respect to the plane where ruthenium is metal-bonded when the ligand L ₉ is bridged and coordinated to ruthenium, and this substituent is When expressed as a number, it is easy to obtain a stable and easily vaporized complex.

As suitable substituents for the substituents R ₃₁ to R ₃₅ of the ligand L ₉ -2, R ₃₁ is preferably any one of an ethyl group, a propyl group, or a butyl group. It is also preferable that R ₃₁ is a branched alkyl group. Specifically, suitable substituents include ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, or tert-butyl group, and are preferred. is an ethyl group, an iso-propyl group, an iso-butyl group, a sec-butyl group, or a tert-butyl group. Further, R ₃₂ , R ₃₃ , R ₃₄ and R ₃₅ may be the same or different from each other, and each is preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom.

The organic ruthenium compounds α, β, and γ as precursors (1) to (3) described above can be used as raw material gases as they are or by heating a solution dissolved in an appropriate solvent.

(I) First film-forming step The first film-forming step is a step of forming a ruthenium thin film or the like on a substrate using the above-described organic ruthenium compounds α, β, and γ as precursors and a non-oxidizing gas as a reaction gas. This film-forming process is an initial stage process of forming a thin film that will become a base such as a ruthenium thin film for manufacturing purposes while suppressing oxidation of the substrate.

The non-oxidizing gas that becomes the reactive gas in the first film forming step is a gas other than the oxidizing gas. Here, oxidizing gas is a gaseous substance that is more likely than air to cause or assist the combustion of other substances by supplying oxygen, and more specifically, the GHS classification falls under Category 1. It is a gaseous substance. In the present invention, preferred non-oxidizing gases include hydrogen, water vapor, ammonia, amine compounds, hydrazine derivatives, and the like.

In addition, the amine compound is a compound represented by "R-NH ₂ ", "RR'-NH", "RR'R"-N", and the substituents R, R', R" in the formula are methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group (2-methylpropyl), sec-butyl group (1-methylpropyl), tert-butyl group (1,1-dimethylethyl), n- Pentyl group, isopentyl group (3-methylbutyl), neopentyl group (2,2-dimethylpropyl), sec-pentyl group (1-methylbutyl), tert-pentyl group (1,1-dimethylpropyl), n-hexyl group, isohexyl group (4-methylpentyl), neohexyl group (2,2-dimethylbutyl), sec-hexyl group (1-methylpentyl), tert-hexyl group (1,1-dimethylpentyl), cyclohexyl group, cyclohexylmethyl group, cyclohexylethyl group, phenyl R, R', and R'' may be the same or different, respectively. R, R', and R'' are more preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group (2-methylpropyl), a sec-butyl group (1-methylpropyl), tert-butyl group (1,1-dimethylethyl), n-pentyl group, isopentyl group (3-methylbutyl), neopentyl group (2,2-dimethylpropyl), sec-pentyl group (1-methylbutyl), tert-pentyl group ( 1,1-dimethylpropyl).

In addition, the hydrazine derivative is a compound represented by "H2N-NRR'", and the substituents R and R' in the formula are hydrogen, methyl group, ethyl group, n-propyl group, isopropyl group, and n-butyl group. , isobutyl group (2-methylpropyl), sec-butyl group (1-methylpropyl), tert-butyl group (1,1-dimethylethyl), n-pentyl group, isopentyl group (3-methylbutyl), neopentyl group (2,2 -dimethylpropyl), sec-pentyl group (1-methylbutyl), tert-pentyl group (1,1-dimethylpropyl), n-hexyl group, isohexyl group (4-methylpentyl), neohexyl group (2,2-dimethylbutyl), sec -hexyl group (1-methylpentyl), tert-hexyl group (1,1-dimethylpentyl), cyclohexyl group, cyclohexylmethyl group, cyclohexylethyl group, phenyl group, benzyl group. R and R' may be the same or different. More preferably, R and R' are hydrogen, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group (2-methylpropyl), sec-butyl group (1-methylpropyl), tert -butyl group (1,1-dimethylbutyl), n-pentyl group, isopentyl group (3-methylbutyl), neopentyl group (2,2-dimethylpropyl), sec-pentyl group (1-methylbutyl), tert-pentyl group (1 , 1-dimethylpropyl).

Further, the thickness of the ruthenium thin film or the like formed in the first film forming step is preferably 2 nm or more and 5 nm or less. Ruthenium thin films formed using non-oxidizing gas tend to contain impurities such as carbon. Therefore, if the film thickness at this stage is made excessively thick, the resistivity of the thin film that has undergone the second film formation process may become high. Furthermore, if the ruthenium thin film or the like formed in the first film formation step is too thin, there is a risk that the substrate will be oxidized in the subsequent second film formation step using an oxidizing gas.

The film-forming conditions in the first film-forming step are arbitrarily set according to the characteristics of the organic ruthenium compounds α, β, and γ, which are precursors. The organic ruthenium compounds α, β, and γ all have relatively high vapor pressures and can be easily vaporized into raw material gas. The heating temperature for vaporizing the precursor to generate the raw material gas is preferably 0° C. or higher and 80° C. or lower.

Further, the film formation temperature during film formation is preferably 150°C or more and 400°C or less. If the temperature is less than 150° C., the decomposition reaction of the organic ruthenium compound will be difficult to proceed, and the progress of film formation will be slow. On the other hand, if the film-forming temperature exceeds 400° C., it becomes difficult to form a uniform film, and there are problems such as damage to the substrate. The film forming temperature is the surface temperature of the substrate, and is usually adjusted by the heating temperature of the substrate.

In the ALD method, as described above, it is assumed that a cycle consisting of an adsorption step, a raw material gas purge step, a reaction step, and a reaction gas purge step is repeated multiple times. At this time, in the second and subsequent cycles, ruthenium etc. may be deposited on the ruthenium thin film etc. of the previous cycle. In this case, although the film is not directly formed on the substrate in this cycle, the cycle is also within the scope of the first film forming process. That is, as long as the reaction gas is a non-oxidizing gas, the second and subsequent cycles are also within the range of the first film forming process.

(II) Second film-forming process The second film-forming process is a process of forming a film using an oxidizing gas as a reactive gas on the ruthenium thin film etc. formed in the above-described first film-forming process. This film-forming process is basically different from the first film-forming process only in the reaction gas. Therefore, the second film forming step can be performed in the same reactor after the first film forming step.

The significance of the oxidizing gas that becomes the reactive gas in the second film forming step is as described above. In the present invention, suitable oxidizing gases include either oxygen or ozone.

The film forming conditions in the second film forming step are also arbitrarily set depending on the characteristics of the organic ruthenium compound which is the precursor. Further, the heating temperature for vaporizing the precursor is preferably 0° C. or more and 80° C. or less, as in the first film forming step. The film-forming temperature during film-forming can be set taking into account that the reaction gas is an oxidizing gas, and can be set within the same range as in the first film-forming step. That is, the film forming temperature is preferably 150°C or more and 400°C or less.

The second film forming step is a step of forming a ruthenium thin film or the like having a desired thickness. Therefore, the thickness of the ruthenium thin film formed in this step is not limited.

Through the first film forming step and second film forming step described above, a ruthenium thin film or the like having a desired thickness is formed. There is no limit to the thickness of the ruthenium thin film or the like formed by the method according to the present invention. For example, in forming a thin ruthenium film of 10 nm class (20 nm or less), it is possible to suppress oxidation of the substrate and optimize the specific resistance of the thin film, compared to conventional film formation using an oxidizing gas. When a substrate is oxidized by an oxidizing gas, the thinner the thin film is, the more it will be affected by the oxidation. By suppressing oxidation of the substrate according to the present invention, a thin film with lower resistance can be obtained. Furthermore, when increasing the film thickness, the film can be formed more efficiently than the conventional film forming method using a non-oxidizing gas as the reaction gas. This is because, after forming the basic thin film in the first film forming step, an oxidizing gas with excellent reactivity is used as a reactive gas.

B. Ruthenium Thin Film According to the Present Invention The present invention also provides a ruthenium thin film or a ruthenium compound thin film formed on a suitable substrate. The ruthenium thin film or the like according to the present invention is oxygen-free on the substrate surface, and even if the film is thin, resistance increase due to substrate oxidation is suppressed. That is, the present invention is a thin film made of ruthenium or a ruthenium compound formed on a substrate, and the thin film does not contain oxygen at the interface with the substrate.

Further, the ruthenium thin film and the like according to the present invention have a reduced impurity content in the thin film. The above-mentioned organic ruthenium compounds contain ligands having carbon as a constituent element, such as carbonyl ligands, and these ligands may be mixed into the thin film during film formation. In the ruthenium thin film and the like according to the present invention, contamination with impurities is also suppressed, and an increase in resistance due to this is also suppressed. In the ruthenium thin film and the like according to the present invention, the average carbon concentration near the outermost surface of the thin film is reduced. Regarding the suppression of impurities in the ruthenium thin film and the like according to the present invention, to explain specifically, the average carbon concentration in the range of 10 nm to 25 nm from the outermost surface of the thin film is reduced to 0.05 atomic % or less.

However, at the interface between the substrate and the thin film, a trace amount of carbon may be included due to film formation using a non-oxidizing gas. Trace carbon is found on the substrate surface (at the interface between the substrate and the thin film). Specifically, the average carbon concentration in a region up to 10 nm from the substrate surface may be 0.2 atomic % or more and 0.5 atomic % or less. The carbon concentration near the substrate surface is more preferably 0.2 atomic % or more and 0.5 atomic % or less in a region up to 5 nm from the substrate surface.
However, since this carbon is in an extremely small amount and is contained near the extreme surface of the substrate, it has little effect on the resistance of the entire thin film.

Further, a structural feature of the ruthenium thin film and the like according to the present invention is that the surface roughness (surface roughness) is reduced. According to the present inventors, when forming a film using a non-oxidizing gas, the delay in nucleation is short, and a thin film with a smooth surface by forming fine crystals tends to be formed. In the present invention, by forming a smooth thin film at an initial stage and then forming a film using an oxidizing gas on the smooth thin film, the surface roughness is lower than that of a thin film formed using only a non-oxidizing gas. Surface scattering, grain boundary scattering, surface roughness, and the like are interrelated factors that affect the specific resistance of a thin film. It is considered that the ruthenium thin film and the like according to the present invention are designed to have a low resistance, particularly by improving surface roughness. Such a reduction in the surface roughness of a thin film can particularly contribute to lowering the resistance of a thin film with a small thickness.

There is no limit to the thickness of the ruthenium thin film or the like according to the present invention. However, since the ruthenium thin film of the present invention suppresses oxidation of the substrate, it is particularly useful for thin films with a thickness of 20 nm or less that can be affected by substrate oxidation.

As explained above, the method of manufacturing a ruthenium thin film or the like by chemical vapor deposition according to the present invention includes a two-step film forming process. The present invention can efficiently form a low-resistance ruthenium thin film or the like by taking advantage of the respective merits of a non-oxidizing gas and an oxidizing gas.

FIG. 2 is a diagram illustrating a manufacturing process of a ruthenium thin film including a two-step film forming process using an ALD method according to an embodiment of the present application. FE-SEM photographs of ruthenium thin films of Example 1 and Example 2 manufactured in the first embodiment. GI-XRD diffraction patterns of ruthenium thin films of Examples 1 and 2 and Comparative Example 1 manufactured in the first embodiment. FIG. 3 is a diagram showing the compositional analysis results in the depth direction of the ruthenium thin films of Example 1 and Comparative Examples 1 and 2 manufactured in the first embodiment. 2 is a graph showing the specific resistance of ruthenium thin films of Examples 1 and 2 and Comparative Examples 1 and 2 manufactured in the first embodiment. 3 is a graph showing the film thickness and specific resistance of ruthenium thin films of Example 3 and Comparative Example 3 manufactured in the second embodiment.

First Embodiment : The best embodiment of the present invention will be described below. In this embodiment, the organic ruthenium compound serving as a precursor is an organic ruthenium compound α, the ligand L ₁ is a trimethylenemethane ligand (L ₁₀ :R=hydrogen), and the ligand X is a carbonyl coordination. Using certain (η ⁴ -methylene-1,3-propanediyl)tricarbonylruthenium (Chemical formula 4), hydrogen was used as a non-oxidizing reaction gas in the first film-forming step, and hydrogen was used as an oxidizing gas in the second film-forming step. A ruthenium thin film was formed by ALD using oxygen as a reactive gas. For comparison, a ruthenium thin film was formed in a single step using a conventional method using only oxygen or hydrogen as a reactive gas.

The precursor (η ⁴ -methylene-1,3-propanediyl)tricarbonylruthenium was synthesized as follows. 50.0 g (97.5 mmol) of tricarbonyl-dichlororuthenium dimer was suspended in 1700 ml of tetrahydrofuran, and 300 ml of a solution of 29.2 g (231.6 mmol) of 3-chloro-2-(chloromethyl)-1-propene in tetrahydrofuran was added. . 19.7 g (800 mmol) of magnesium chips were slowly added, and the mixture was allowed to react at room temperature for 3 hours. The reaction mixture was quenched by adding 5 mL of methanol, and the solvent was distilled off under reduced pressure. The resulting residue was extracted three times with 30 mL of pentane, and the solvent was distilled off under reduced pressure. The obtained oil was purified by sublimation to obtain 16.3 g (68.3 mmol) of a colorless liquid as the target product (yield 35%). The synthesis reaction of this organic ruthenium compound is as follows.

[Formation of ruthenium thin film]
FIG. 1 shows the flow of the manufacturing process of a ruthenium thin film by the ALD method in this embodiment. As explained above, the film formation process using the ALD method includes (i) an adsorption step in which source gas is introduced to the substrate, (ii) a source gas purge step in which excess source gas is exhausted, and (iii) a reaction gas is introduced. It consists of a reaction step for forming a thin film, and (iv) a reaction gas purge step for exhausting excess reaction gas. These steps are then repeated as one cycle until the target film thickness is achieved.

In this embodiment, a ruthenium thin film was formed using a Si substrate (2 cm x 2 cm) having a TiN film (thickness 20 nm) on the surface as a substrate for film formation. The film forming conditions in the first and second film forming steps were as follows.

(I) First film formation step (i) Raw material gas introduction step/raw material heating temperature: 10°C
・Carrier gas: Nitrogen (50sccm)
・Introduction time: 5 seconds (ii) Raw material gas purge step ・Purge gas: Nitrogen (100sccm)
・Introduction time: 20 seconds (iii) Reaction gas introduction step ・Reaction gas: Hydrogen (50 sccm)
・Introduction time: 30 seconds (iv) Reaction gas purge step ・Purge gas: Nitrogen (100sccm)
・Introduction time: 10 seconds

(II) Second film forming step (i) Raw material gas introduction step/raw material heating temperature: 10°C
・Carrier gas: Nitrogen (50sccm)
・Introduction time: 10 seconds (ii) Raw material gas purge step ・Purge gas: Nitrogen (100sccm)
・Introduction time: 10 seconds (iii) Reaction gas introduction step ・Reaction gas: Oxygen (50 sccm)
・Introduction time: 10 seconds (iv) Reaction gas purge step ・Purge gas: Nitrogen (100sccm)
・Introduction time: 10 seconds

In this embodiment, the thickness of the ruthenium thin film formed in the first film forming step (reactive gas: hydrogen) was set to 2 nm (Example 1) and 4 nm (Example 2). Then, in the second film forming step (reactive gas: oxygen), a ruthenium thin film was formed to a final film thickness of 40 nm (Example 1: 38 nm film formed, Example 2: 36 nm film formed).

Further, as a comparative example, a ruthenium thin film was formed by a one-step ALD method using only oxygen (Comparative Example 1) or only hydrogen (Comparative Example 2) as a reaction gas. In these comparative examples, a 40 nm ruthenium thin film was formed by controlling the number of cycles under the same conditions as in the first and second film forming steps described above.

FIG. 2 shows FE-SEM (field emission scanning electron microscope) cross-sectional photographs of the ruthenium thin films of Examples 1 and 2 of the present embodiment. Further, FIG. 3 shows XRD diffraction patterns of the ruthenium thin films of Examples 1 and 2 and Comparative Example 1 by GI-XRD (small angle incidence X-ray diffraction). Regarding the crystallinity of the ruthenium thin film, it can be said that the ruthenium thin film formed by the two-step film formation of this embodiment is equivalent to the conventional one-step film formation. When the crystal grain size of each ruthenium thin film was calculated from the GI-XRD results, it was 29.3 nm for Example 1, 28.5 nm for Example 2, and 32.2 nm for Comparative Example 1. It can be said that Examples 1 and 2 in which the film was formed using hydrogen in the first film forming step had smaller particle sizes than Comparative Example 1 in which the film was formed using only oxygen. As described above, since the delay in nucleation is short in film formation using a non-oxidizing gas, fine crystal grains are formed quickly. It is considered that in Examples 1 and 2, thin films were grown on the fine ruthenium crystals formed in this manner. When the surface roughness of Example 1 and Comparative Example 1 was observed using an atomic force microscope, it was found that Comparative Example 1 had a surface roughness of 2.0 nm, while Example 1 had a surface roughness of 1.8 nm. It was confirmed that it was reduced.

Further, FIG. 4 shows the results of composition analysis in the depth direction by SIMS (secondary ion mass spectrometry) performed on the ruthenium thin films of Example 1, Comparative Example 1, and Comparative Example 2. In the ruthenium thin film formed in one step using only hydrogen in Comparative Example 2, it was confirmed that carbon (C) was present at the substrate interface and in the film. In the case of the ruthenium thin film formed in one step using only oxygen in Comparative Example 2, no carbon content was observed in the film. Also in Example 1, no carbon content was observed in the film. Furthermore, when comparing Example 1 and Comparative Example 1, it is confirmed that Comparative Example 1 has the presence of oxygen (O) at the interface with the substrate, although it is slight. Referring to these, the two-step film formation using hydrogen and oxygen in Example 1 suppresses the mixing of oxygen at the substrate interface (substrate oxidation) and the mixing of carbon in the film, and produces a high-purity ruthenium thin film. It can be said that it can be manufactured.

Next, the specific resistance of the ruthenium thin films of Examples 1 and 2 and Comparative Examples 1 and 2 was measured. The specific resistance was measured using a four-probe method. The results of this measurement are shown in FIG. Comparative Example 2 had the highest specific resistance among these ruthenium thin films. As mentioned above, the ruthenium thin film formed using hydrogen, which is a non-oxidizing gas, contains impurities such as carbon, which is considered to have increased the specific resistance. As a result, Comparative Example 1 is considered to have a higher specific resistance than the ruthenium thin film made of oxygen in Comparative Example 1.

In contrast to these comparative examples, the ruthenium thin film formed by the two-step film forming process of Example 1 has a lower specific resistance than the ruthenium thin film formed by oxygen of Comparative Example 1. It can be said that we were able to reduce the resistance of the thin film as a result of suppressing oxidation of the substrate by applying hydrogen in the first film-forming process, and as a result of rapid film-forming reaction and impurity release due to the application of oxygen in the second film-forming process. . Furthermore, although the specific resistance of Example 2 is higher than that of Comparative Example 1, the difference is slight and is at the same level. Example 2 has good results similar to Example 1, considering that concerns about damage due to substrate oxidation can be almost completely eliminated by applying a non-oxidizing gas in the first film forming step. It can be said. The evaluation of Example 2 can be supported because this thin film clearly had a lower specific resistance than the thin film of Comparative Example 2.

Second Embodiment : In this embodiment, a two-step film forming process was applied and changes in specific resistance were studied when the thickness of the ruthenium thin film was increased. Under the same conditions as in the first embodiment, a 2 nm thin ruthenium film was formed in the first film forming step (reactive gas: hydrogen), and a ruthenium thin film was formed in the second film forming step (reactive gas: oxygen). At this time, ruthenium thin films were formed with final film thicknesses of 5 nm, 12 nm, 18 nm, and 23 nm in the second film forming step (Example 3). Then, the specific resistance of the ruthenium thin film of each thickness was measured.

In addition, as a comparative example of this Example 3, 6 nm, 10 nm, 15 nm, and 20 nm ruthenium thin films were formed in a one-step film forming process using oxygen as the reaction gas, and the specific resistance was measured (Comparative Example 3) .

The measurement results of the specific resistance of these ruthenium thin films are shown in FIG. From FIG. 6, the ruthenium thin film (Example 3) formed by a two-step film formation process has a specific resistance equal to or lower than that of the ruthenium thin film (Comparative Example 3) formed by a one-step film formation process using oxygen as the reactive gas. This is confirmed. In particular, in the case of a thin film having a small thickness (12 nm or less), a thin film formed in a two-step film forming process has a lower specific resistance. This is thought to be due to the suppression of oxidation of the substrate by the application of non-oxidizing gas in the first film forming step and the reduction in surface roughness due to the small particle size. The reduction in resistance of such ultra-thin ruthenium thin films is thought to be useful in thin film electrodes of semiconductor devices, which are becoming increasingly miniaturized.

As described above, the method for producing a ruthenium thin film or the like using a two-step film forming process according to the present invention can form a high-quality, low-resistivity ruthenium thin film or the like while suppressing oxidation of the substrate. The present invention is suitable for use as a wiring/electrode material for semiconductor devices such as DRAMs. In particular, it is possible to cope with miniaturization of wiring in ultra-miniature semiconductor devices.

Claims (7)

In a method for producing a ruthenium thin film or a ruthenium compound thin film by a chemical vapor deposition method in which an organic ruthenium compound and a reactive gas are reacted on a substrate to form a ruthenium thin film or a ruthenium compound thin film,
A first film forming step of introducing a non-oxidizing gas as the reactive gas and forming a ruthenium thin film or a ruthenium compound thin film on the substrate surface;
After the film formation in the first film formation step, a second film formation step of introducing an oxidizing gas as the reaction gas to form a ruthenium thin film or a ruthenium compound thin film,
Ruthenium characterized in that any one of the following organic ruthenium compounds α, β, and γ of (1) to (3) is applied as the organic ruthenium compound introduced in the first film forming step and the second film forming step. A method for producing a thin film or a ruthenium compound thin film.
(1) Organic ruthenium compound α

(In the formula, the ligand L ₁ is a linear or branched chain hydrocarbon group or a cyclic hydrocarbon group having 2 to 13 carbon atoms. Also, the ligand X is a carbonyl ligand (CO) or isocyanide ligands (L ₂ ), pyridine ligands (L ₃ ), amine ligands (L ₄ ), imidazole ligands (L _{5 )} represented by the following formulas ), a pyridazine ligand (L ₆ ), a pyrimidine ligand (L ₇ ), or a pyrazine ligand (L ₈ ).

(In the above formula, the substituent R ₁ of the isocyanide ligand L ₂ is hydrogen, a linear or branched alkyl group having 1 to 8 carbon atoms, or a cyclic alkyl group having 3 to 9 carbon atoms, or a cyclic alkyl group having 3 to 9 carbon atoms. A straight chain or branched amino group having 1 to 8 carbon atoms, an aryl group having 6 to 9 carbon atoms, a straight chain or branched alkoxy group having 1 to 8 carbon atoms, a straight chain or branched chain having 1 to 8 carbon atoms, (A branched cyano group, a straight or branched nitro group having 1 to 8 carbon atoms, or a straight or branched fluoroalkyl group having 1 to 8 carbon atoms.)

(In the above formula, substituents R ₂ to R ₆ of the pyridine ligand L ₃ are hydrogen, a linear or branched alkyl group or fluoroalkyl group having 1 to 5 carbon atoms, and 1 to 5 carbon atoms, respectively. The following straight-chain or branched fluoro groups, straight-chain or branched alkoxy groups with 1 to 5 carbon atoms, straight-chain or branched cyano groups with 1 to 5 carbon atoms, and straight-chain or branched cyano groups with 1 to 5 carbon atoms. Either a straight-chain or branched nitro group.)

(In the above formula, each of the substituents R ₇ to R ₉ of the amine ligand L ₄ is a linear or branched alkyl group having 1 to 5 carbon atoms.)

(In the above formula, the substituent R ₁₀ of the imidazole ligand L ₅ is hydrogen, a linear or branched alkyl group having 1 to 8 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, or a carbon number 1 Any of the above 8 or less linear or branched fluoroalkyl groups. Substituents R ₁₁ to R ₁₃ are hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and carbon atoms. Straight chain or branched amino group having 1 to 5 carbon atoms, straight chain or branched alkoxy group having 1 to 5 carbon atoms, straight chain or branched cyano group having 1 to 5 carbon atoms, 1 carbon number Any of a linear or branched nitro group having 5 or more carbon atoms, a linear or branched fluoro group having 1 to 5 carbon atoms, or a linear or branched fluoroalkyl group having 1 to 5 carbon atoms. be.)

(In the above formula, substituents R ₁₄ to R ₁₇ of the pyridazine ligand L ₆ are hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and a linear or branched alkyl group having 1 to 5 carbon atoms, respectively. or a branched fluoroalkyl group, a linear or branched fluoro group having 1 to 5 carbon atoms, hydrogen or a linear or branched alkoxy group having 1 to 5 carbon atoms, hydrogen or a linear or branched alkoxy group having 1 to 5 carbon atoms; is either a straight-chain or branched cyano group, hydrogen, or a straight-chain or branched nitro group having 1 to 5 carbon atoms.)

(In the above formula, the substituents R ₁₈ to R ₂₁ of the pyrimidine ligand L ₇ are hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and a linear or branched alkyl group having 1 to 5 carbon atoms, respectively. or a branched fluoroalkyl group, a linear or branched fluoro group having 1 to 5 carbon atoms, a linear or branched alkoxy group having 1 to 5 carbon atoms, a linear or branched chain having 1 to 5 carbon atoms, or Either a branched cyano group or a straight or branched nitro group having 1 to 5 carbon atoms.)

(In the above formula, substituents R ₂₂ to R ₂₅ of pyrazine ligand L ₈ are hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, and a linear or branched alkyl group having 1 to 5 carbon atoms, respectively. or a branched fluoroalkyl group, a linear or branched fluoro group having 1 to 5 carbon atoms, a linear or branched alkoxy group having 1 to 5 carbon atoms, a linear or branched chain having 1 to 5 carbon atoms, or Either a branched cyano group or a straight or branched nitro group having 1 to 5 carbon atoms.)
(2) Organic ruthenium compound β

(In the formula, R ₂₆ and R ₂₇ may be the same or different, and are each one of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms.)
(3) Organic ruthenium compound γ

(In the formula, the ligand L ₉ is a ligand represented by either (L ₉ -1) or (L ₉ -2) shown in the following formula, and a ligand containing one nitrogen atom. )

(In the formula, * is the position of the atom that bridges and coordinates to ruthenium. _{R 28} to R ₃₅ may be the same or different, and each represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and (1 type) 2. The method for producing a ruthenium thin film or a ruthenium compound thin film according to claim 1, wherein the organic ruthenium compound introduced in the first film forming step and the second film forming step is the following organic ruthenium compound.

(In the formula, the ligand L ₁₀ is represented by the following formula 13. It is a trimethylenemethane-based ligand.

(In the above formula, the substituent R of trimethylenemethane ligand L ₁₀ is hydrogen, a linear or branched alkyl group having 1 to 8 carbon atoms, a cyclic alkyl group having 3 to 9 carbon atoms, and a carbon number Straight chain or branched alkenyl group with 2 to 8 carbon atoms, straight chain or branched alkynyl group with 2 to 8 carbon atoms, straight chain or branched chain amino group with 2 to 8 carbon atoms, 6 or more carbon atoms 9 or less aryl group.) 3. The method for producing a ruthenium thin film or ruthenium compound thin film according to claim 1 or 2, wherein the non-oxidizing gas in the first film forming step is hydrogen, water vapor, ammonia, organic amines, or hydrazine derivatives. 3. The method for producing a ruthenium thin film or ruthenium compound thin film according to claim 1 or 2, wherein the oxidizing gas in the second film forming step is either oxygen or ozone. 4. The method for producing a ruthenium thin film or ruthenium compound thin film according to claim 3, wherein the oxidizing gas in the second film forming step is either oxygen or ozone. 3. The method for producing a ruthenium thin film or ruthenium compound thin film according to claim 1 or 2, wherein the ruthenium thin film or ruthenium compound thin film is formed in the first film forming step to a thickness in the range of 2 nm or more and 5 nm or less. A thin film made of ruthenium or a ruthenium compound formed on a substrate,
The thin film is a thin film that does not contain oxygen at the interface with the substrate.

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